Re: [PATCH 05/11] drm/mediatek: ovl: Implement support for Inverse Gamma
From: CK Hu (胡俊光) <hidden>
Date: 2026-02-25 08:54:18
Also in:
dri-devel, linux-mediatek, lkml
On Tue, 2025-12-23 at 16:44 -0300, Nícolas F. R. A. Prado wrote:
External email : Please do not click links or open attachments until you have verified the sender or the content. The OVL hardware allows selecting between different fixed transfer functions for each layer through the Inverse Gamma setting. Available functions are scRGB and BT.709. Implement support for it and expose it as a colorop through the DRM plane color pipeline uAPI. Signed-off-by: Nícolas F. R. A. Prado <redacted> ---
[snip]
quoted hunk ↗ jump to hunk
#include <linux/clk.h> #include <linux/component.h>@@ -47,6 +50,12 @@ #define OVL_CON_CLRFMT_BIT_DEPTH(depth, n) ((depth) << (4 * (n))) #define OVL_CON_CLRFMT_8_BIT (0) #define OVL_CON_CLRFMT_10_BIT (1) +#define DISP_REG_OVL_WCG_CFG1 0x2d8 +#define IGAMMA_EN(layer) BIT(0 + 4 * (layer))
BIT(4 * (layer))
quoted hunk ↗ jump to hunk
+#define DISP_REG_OVL_WCG_CFG2 0x2dc +#define IGAMMA_MASK(layer) GENMASK((layer) * 4 + 1, (layer) * 4) +#define IGAMMA_SCRGB 0 +#define IGAMMA_BT709 1 #define DISP_REG_OVL_ADDR_MT8173 0x0f40 #define DISP_REG_OVL_ADDR(ovl, n) ((ovl)->data->addr + 0x20 * (n)) #define DISP_REG_OVL_HDR_ADDR(ovl, n) ((ovl)->data->addr + 0x20 * (n) + 0x04)@@ -492,6 +501,91 @@ static void mtk_ovl_afbc_layer_config(struct mtk_disp_ovl *ovl, } } +static int mtk_ovl_colorop_curve_to_reg_val(enum drm_colorop_curve_1d_type curve) +{ + switch (curve) { + case DRM_COLOROP_1D_CURVE_SRGB_INV_EOTF: + return IGAMMA_SCRGB; + case DRM_COLOROP_1D_CURVE_BT2020_OETF:
I don't exactly know what DRM_COLOROP_1D_CURVE_BT2020_OETF mean, but there is DRM_COLOROP_1D_CURVE_BT2020_INV_OETF. This patch is about inverse gamma, so this should be DRM_COLOROP_1D_CURVE_BT2020_INV_OETF?
+ return IGAMMA_BT709;
+ default:
+ return -EINVAL;
+ }
+}
+
+static void mtk_ovl_apply_igamma(struct mtk_disp_ovl *ovl, unsigned int idx,
+ struct drm_colorop *colorop,
+ struct cmdq_pkt *cmdq_pkt)
+{
+ int curve_reg_val;
+
+ if (colorop->state->bypass) {
+ /* igamma curve needs to be set to default when igamma is disabled */
+ curve_reg_val = IGAMMA_SCRGB;
I would like to set igamma curve after disable.
So
if (colorop->state->bypass) {
mtk_ovl_disable_colorops();
return;
}
+ } else {
+ curve_reg_val = mtk_ovl_colorop_curve_to_reg_val(colorop->state->curve_1d_type);
+ if (curve_reg_val < 0) {
+ drm_WARN(ovl->crtc->dev, 1,
+ "Invalid curve 1d type %u\n",
+ colorop->state->curve_1d_type);
+ return;
+ }
+ }
+
+ mtk_ddp_write_mask(cmdq_pkt,
+ field_prep(IGAMMA_MASK(idx), curve_reg_val),
+ &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_WCG_CFG2,
+ IGAMMA_MASK(idx));
+
+ mtk_ddp_write_mask(cmdq_pkt,
+ colorop->state->bypass ? 0 : IGAMMA_EN(idx),
+ &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_WCG_CFG1,
+ IGAMMA_EN(idx));
+}
+[snip]
+static const struct drm_colorop_funcs mtk_ovl_colorop_funcs = {
+ .destroy = drm_colorop_destroy,
+};
+
+static const u64 igamma_supported_tfs =
+ BIT(DRM_COLOROP_1D_CURVE_SRGB_INV_EOTF) |
+ BIT(DRM_COLOROP_1D_CURVE_BT2020_OETF);
+
+#define MAX_COLOR_PIPELINE_OPS 3Why is 3? Is this hardware limitation? Provide some information about this value, so we know it's possible to change it or not.
+
+static int
+mtk_ovl_initialize_plane_color_pipeline(struct drm_plane *plane,
+ struct drm_prop_enum_list *pipeline)
+{
+ struct drm_colorop *ops[MAX_COLOR_PIPELINE_OPS];
+ struct drm_device *dev = plane->dev;
+ int i = 0;
+ int ret;
+
+ memset(ops, 0, sizeof(ops));
+
+ /* 1st op: OVL's Inverse Gamma */
+ ops[i] = kzalloc(sizeof(*ops[i]), GFP_KERNEL);
+ if (!ops[i]) {
+ ret = -ENOMEM;
+ goto err_alloc;
+ }
+
+ ret = drm_plane_colorop_curve_1d_init(dev, ops[i], plane,
+ &mtk_ovl_colorop_funcs,
+ igamma_supported_tfs,
+ DRM_COLOROP_FLAG_ALLOW_BYPASS);If other sub driver (maybe ovl adapter) also has inverse gamma, most part of this function looks common and only mtk_ovl_colorop_funcs and igamma_supported_tfs are sub driver specific. So move the common part to mtk_crtc.c and sub driver provide function to query mtk_ovl_colorop_funcs and igamma_supported_tfs. (mtk_ovl_colorop_funcs looks not a sub driver specific function, maybe it could be common part) Regards, CK
+ if (ret)
+ goto err_colorop_init;
+
+ pipeline->type = ops[0]->base.id;
+ pipeline->name = kasprintf(GFP_KERNEL, "Color Pipeline %d", ops[0]->base.id);
+
+ return 0;
+
+err_colorop_init:
+ kfree(ops[i]);
+
+err_alloc:
+ i--;
+ for (; i >= 0; i--) {
+ drm_colorop_cleanup(ops[i]);
+ kfree(ops[i]);
+ }
+
+ return ret;
+}
+